The invention relates in general to a group control for elevators and, in particular, to a group control with immediate assignment of calls of destination.
Many known elevator group control systems include call registering devices located at the floors, by means of which calls for desired floors of destination can be entered. The entered calls are stored in floor and car call memories assigned to the elevators of the group where a call characterizing the entry floor is stored in the floor call memory and the calls characterizing the destination floors are stored in the car call register memory. Selectors assigned to each elevator of the group indicate the floor of a possible stop. First and second scanners are assigned to each elevator of the group. The first scanner operates during a cost of operation calculation cycle to store for each floor the costs in a cost memory. The second scanner operates during a cost comparison cycle of the costs for all elevators by means of which the entered call is assigned to the car of the elevator group which exhibits the lowest operating costs.
In such group controls, as for example shown in the European patent no. EP-B 0 032 213, operating costs corresponding to the waiting times of passengers are calculated from data specific to each of the elevators and compared one with the other for the purpose of ascertaining the elevator best able to serve a certain floor. An important factor of the operating costs is due to the car calls which, in controls of that kind, are known only for the instantaneous trip traveled by the car. It therefore appears undesirable to allocate floor calls which are, for example, entered behind the car in the same direction of travel since the operating costs determined in the trip taking place would be wrong for a subsequent trip. Therefore, calls of that kind could at most be fed to a waiting queue, wherein it should be indicated by suitable signaling to the passenger waiting at the floor concerned that his call is not yet allocated and an indefinite waiting time must be accepted. If the waiting queue is already filled with calls which, for example due to overloading, could not be allocated, then correspondingly longer waiting times must be reckoned with.
Another elevator group control is shown in European patent no. EP-A 0 246 395, in which the destination floor can be entered at the entry floor. This control registers a call for the input floor and a call for the destination floor so that, by contrast to the group control described in the previous paragraph, the operating costs of calls of subsequent trip of the car can be ascertained more readily. Since the numbers of boarding passengers and alighting passengers, which are important for the calculation of the operating costs, are merely probable values derived from the experiences of the past, the operating costs, which correspond to the lost times of passengers probably situated in the car when serving a new call, can be ascertained only approximately. When the probable number of passengers in the car is not determinable with sufficient accuracy, no decision can be made with respect to an overload on assignment of a new call. In addition, an assignment of calls for a subsequent trip is not possible when the destination floor entered at a floor lying behind the car in direction of travel lies in front of the car, so that calls of that kind would have to be fed to a waiting queue.
An improvement in the call assignment criteria, particularly with a view of avoidance of overload for a floor to be allocated, is proposed in the European patent application no. EP-PA 88106273.1. It is suggested to replace the probable numbers of boarding and alighting passengers by those actually to be expected. In this case, a sum is formed from the number of the calls entered at a floor and the number of the calls designating this floor as a destination floor and stored as a load value in a load memory, wherein the load value is interpreted in the calculation as the number of passengers which would be situated in the car on the departure from the floor concerned.